EFFECTS OF INDOLINIC AND QUINOLINIC AMINOXYLS ON PROTEIN AND LIPID-PEROXIDATION OF RAT-LIVER MICROSOMES

A study on peroxyl radical induced oxidation of rat liver microsomal m embranes in the presence of different indolinic and quinolinic aminoxy ls (Scheme 1) was carried out in order to test their efficiency as ant ioxidants in lipid and protein peroxidation. The extent of lipid perox idation was quantified by the amount of malondialdehyde (MDA) produced , and the measurement of carbonyl residues was used as an index of mic rosomal protein oxidation. The results obtained suggest that lipid sol uble indolinic and quinolinic aminoxyls are efficient in protecting li pids and proteins of biological membranes against oxidation. The effic acy of these aminoxyls as protectors of lipids and proteins was much h igher than the water soluble TEMPOL. Moreover, the hydrophobic aminoxy ls were more effective in preventing protein than lipid oxidation at l ow concentrations (1-20 mu M). However, at high concentration (100 mu M), lipid as opposed to protein oxidation was almost completely inhibi ted. The data supports the hypothesis that proteins probably have a di fferent oxidation pattern from lipids.